1. Field of the Invention
The invention relates to a method of contact formation in the fabrication of integrated circuits, and more particularly, to a method of forming an amorphous silicon glue layer for improved contact formation in the manufacture of integrated circuits.
2. Description of the Prior Art
In a common application for integrated circuit fabrication, a contact opening is etched through an insulating layer to an underlying conductive area to which electrical contact is to be made. A glue layer, typically titanium, is conformally deposited within the contact opening. Next, a titanium nitride barrier layer is formed within the contact opening. A conducting layer material is deposited within the contact opening. Typically, tungsten is deposited and etched back to form a plug filling the contact opening. After tungsten deposition, the wafer is subjected to annealing whereby the titanium glue layer reacts with the silicon substrate to form titanium silicide. Silicon is lost from the substrate both during etching and in the reaction with the titanium layer. As the design rules continue to shrink, contact depth becomes more shallow. It is difficult to decrease the depth of the titanium silicide region. This may lead to the penetration of the junction layer by the titanium silicide region causing junction leakage. Increased contact resistance is also a concern.
U.S. Pat. No. 5,510,296 to Yen et al teaches a method of contact formation including an amorphous silicon glue layer and a deposited tungsten silicide layer to complete the contact which is subjected to a high flow rate nitrogen annealing to provide a contact with low contact resistance. U.S. Pat. No. 5,397,742 to Kim a titanium and titanium nitride barrier layer followed by the deposition of titanium and polysilicon layers which are annealed to form titanium silicide. A tungsten plug is then formed within the contact opening. U.S. Pat. No. 5,427,981 to Choi teaches the formation of a polysilicon and photoresist layer at the bottom of a contact opening. Titanium is deposited and annealed to react with the polysilicon layer to form titanium silicide. Tungsten is deposited over the titanium silicide layer at the bottom of the contact opening.